An Optical Transport Network (OTN) is a core technology of a transport network. The OTN has robust operation administration and maintenance (OAM) capabilities, a strong Tandem Connection Monitoring (TCM) capability, an out-of-band Forward Error Correction (FEC) capability, and can implement flexible scheduling and management of large-capacity services.
The OTN standardization system defines four Optical Channel Transport Units (OTUs) with fixed line rates. For example, the OTN standardization system defines an OTU1, an OTU2, an OTU3, and an OTU4, whose line rate levels are respectively 2.5 gigabits per second (Gbit/s), 10 Gbit/s, 40 Gbit/s, and 100 Gbit/s. The four OTUs respectively correspond to four Optical Channel Data Units (ODUs) of same rate levels: an ODU1, an ODU2, an ODU3, and an ODU4. The four ODUs respectively correspond to four Optical Channel Payload Units (OPUs) of same rate levels: an OPU1, an OPU2, an OPU3, and an OPU4.
With development of applications such as the Internet and cloud computing, information traffic in a network increases exponentially. Thus, it is desirable that the OTN provide more available bandwidth, and the OTN being developed to higher transfer rates, for example, 400 Gbit/s or 1 TGbit/s.
Currently, the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) is formulating an OTUCn (where C is a roman numeral for 100, and n is a positive integer) interface for beyond-100 G OTN applications. The OTUCn interface can provide an electrical interface processing capability of an n*100 G rate. An OTUCn frame consists of n OTU subframes. The OTUCn frame is managed and monitored as one signal, and provides a network management function at an optical channel transport unit level. Correspondingly, there are an ODUCn and an OPUCn of a rate of n*100 G. An ODUCn overhead is added to an OPUCn frame to form an ODUCn frame, and a Frame Alignment (FA) overhead and an OTUCn overhead are added to the ODUCn frame to form an OTUCn frame. After the OTUCn frame is modulated by an optical module matching a rate corresponding to the OTUCn frame, a serial OTUCn bit data flow is formed, and the serial OTUCn bit data flow is sent by using one way of optical fiber.
In the current system, the ODUCn is mapped to an OTUCn having a same rate as the ODUCn, and the OTUCn is sent only after being modulated by an optical module at a same rate as the OTUCn. Therefore, to send ODUCns of different rates, optical modules of different rates are used to perform modulation. Further, in the current system, to send optical channel unit signals of different rates, optical modules of different rates are used to perform modulation. This results in high network costs.